AP
In a letter to Intelligence Committee Chair Dianne Feinstein (D-Calif.) that was made public Tuesday,
"My response was clearly erroneous - for which I apologize," Clapper wrote in the letter, which was dated June 21.
Clapper's original statement has become a source of major controversy in light of the revelations of the NSA's surveillance programs, which have been exposed in a series of leaks from 30-year-old former NSA contractor Edward Snowden.
During the March 12, hearing Wyden asked Clapper, "Does the NSA collect any type of data at all on millions or hundreds of millions of Americans?"
"No, sir," Clapper replied.
"It does not?" Wyden said, sounding somewhat surprised.
"Not wittingly," Clapper added. "There are cases where they could inadvertently, perhaps, collect, but not wittingly."
In the letter to Feinstein, Clapper explained the late addition to his original statement by saying that he realized Wyden was referring to collection of metadata - not content collection. Clapper said he thought Wyden was referring to Section 702 of the Federal Intelligence Surveillance Act, which permits the NSA to collect information on certain people outside of the United States - not the domestic data collection allowed under Section 215 of the Patriot Act.
"While my staff acknowledged the error to Senator Wyden's staff soon after the hearing, I can now openly correct it because the existence of the metadata program has been declassified," Clapper wrote.
"Mistakes will happen, and when I make one, I correct it."
The full letter is below: